(1) Field of the Invention
The present invention relates to a film formation apparatus, and particularly relates to improved technology of a thin film semiconductor manufacturing apparatus in an inductive coupling method, in which a thin film semiconductor is manufactured using a plasma enhanced chemical vapor deposition (plasma CVD) method or a plasma etching method.
(2) Description of the Related Art
Recently, flat panel displays (FPDs) have been widely used and it is desirable that their panels are upsized as their uses are increased. Accompanied by such a situation, it is required to efficiently fabricate good quality of electronic devices (thin film semiconductors) such as thin film transistors (TFTs) on the surface of a large-sized substrate in manufacturing processes of FPDs such as liquid crystal displays (LCDs) or organic EL displays (OELDs).
Among methods for fabricating thin film semiconductors on the large-sized substrate, there are a plasma CVD method and a plasma etching method. In these methods, a plasma is generated in an enclosed space by exciting an excitable gas containing inert gases and then a film formation gas is added, whereby a chemical reaction (gas reaction) is induced so that a thin film is formed on the surface of the substrate.
Here, there are two types of the plasma CVD methods: a capacitive coupling method, and an inductive coupling method.
The capacitive coupling method of the plasma CVD methods is configured so that a substrate setting table and an electrode plate are placed so as to face each other, between which a plasma is generated. Gas reactions are excited by tree radicals and the like generated with the plasma, so that a thin film is deposited on the surface of the substrate placed on the substrate setting table.
In this capacitive coupling method, a scale of plasma is in proportion to the surface area of the electrode plate. Therefore, this method has an advantage that a thin film can be formed on the relatively large area at one time by increasing the size of the electrode plate. However, since the plasma density is not so high and approximately 1016 mxe2x88x923, a high film formation rate cannot be expected. In addition, the capacitive coupling method is configured so that a plasma spreading over the reaction zone in the apparatus and a substrate are separated from each other by a sheath formed with a self-bias voltage. As such, if positive ions in the plasma are accelerated by the bias voltage and collide with the substrate surface, a uniform film thickness cannot be obtained, which is a serious problem in the method.
In contrast, the inductive coupling method of the plasma CVD methods is configured so that, in one example, a workcoil is wound about a cylindrical-shaped tube, a plasma is generated in the cylindrical-shaped tube by a magnetic field produced by electrically charging the workcoil, and a thin film is formed on the substrate surface by exciting gas reactions with the plasma.
This inductive coupling method has an advantage that a plasma with a high density (ranging from approximately 1017 to 1018 mxe2x88x923) and abundant free radicals can be obtained, so that a film formation rate is higher than the capacitive coupling method and the manufacturability of films is excellent. However, this inductive coupling method is generally not suitable for the film formation in a relatively large area due to structural properties of the film formation apparatus. That is, even when a large-sized coil is employed according to the substrate size, a good quality of plasma is difficult to obtain because of a non-uniform distribution of the magnetic density generated by the large-sized coil.
Meanwhile, the plasma etching method is a film formation method, in which a thin film of a desired pattern is formed by allowing radicals generated with plasma to chemically react with a substrate surface to be etched. Here, this plasma may be produced by either the capacitive coupling method or the inductive coupling method as stated above. However, the scale and efficiency of etching considerably depend on the properties of above stated film formation apparatuses, so the current plasma etching method is not regarded as a technique for obtaining a good quality of patterned thin films.
As stated above, it cannot be said that a thin film formation apparatus which forms uniform thin films in a relatively large area has been established.
The film formation techniques such as the plasma CVD method and the plasma etching method are originally used for a fine patterned circuit in a small size substrate to fabricate LSIs and so on, while film formation techniques have not been yet established for large-sized FPDs.
The object of the present invention is to provide a film formation apparatus in a plasma CVD method and a plasma etching method making use of an inductive coupling method, by which a good quality of thin film can be formed in a large area and at a relatively high rate, as compared with the conventional film formation apparatus.
The above object can be achieved by the film formation apparatus made up of: a plurality of plasma generators; two or more film formation gas discharge means; and a substrate setting means; wherein the plurality of plasma generators are inductive coupling types, the substrate setting means faces the plurality of plasma generators across a reaction zone, and one or more film formation gas discharge means is included in each of two movable members which perform reciprocating motions on axes intersecting each other and parallel to a top surface of a film formation target substrate placed on the substrate setting means.
By means of the above structure, a plasma with a relatively high density can be formed in a large area without nonuniformity and a film formation gas excited by free radicals in the plasma can uniformly spread all over the surface of the film formation target on the substrate, so that a film formation process with a high deposition rate can be realized. As a result, a large-sized substrate on which a good quality of thin film is formed can be provided.